There are four basic types of compression spring ends, as shown. The type of ends specified affect the pitch, solid height, number of active and total coils, free length, and seating characteristics of the spring.

OPEN END: the coils are consistent with no pitch change through the end of the spring.

CLOSED ENDS, NOT GROUND: the end coils' pitch is reduced so the end coils touch.

OPEN & GROUND: last coil ground ‘flat’ in appearance and has a less parallel end